Co-Immunoprecipitation (Co-IP) and Pull-Down

The pull-down assay is a robust method by which a target protein is extracted from a mixture (e.g., cell lysate or serum) via its affinity to a specially prepared solid support. It is often possible to detect macromolecules that form stable complexes with the target protein in a pull-down assay—when the pull-down is accomplished using immobilized antibody, the method is known as coimmunoprecipitation (co-IP). After co-IP, immobilized immune complexes can be collected, eluted from the support, and identified, thereby revealing the composition of the retrieved multimers.

Popular co-IP and pull-down products

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Dynabeads Co-Immunoprecipitation Kit

This co-IP kit is ideal for maintaining protein complexes during pull-down.

“Dynabeads are absolutely the best technology we have found so far for pulling out large complexes.”
Dr Michael P. Rout, Rockefeller University

If you are using techniques such as Sepharose® beads and spin columns for pull-down, note that your protein complexes can dissociate from exposure to large surfaces, mechanical strain (e.g., centrifugation), dilution, and excessive handling (pre-clearing). Use the Dynabeads Co-Immunoprecipitation Kit (Cat. No. 14321D) to help ensure better preservation of native protein conformations and large protein interaction complexes. Just couple your antibody directly to the beads, and use the magnet to separate your protein complexes. Although some researchers choose to pre-clear using Sepharose® beads, non-specific binding can result in a contamination of the final product. Skip unnecessary steps and help ensure you obtain intact protein complexes.

Advantages of Dynabeads products for protein complex isolation

  • Quick and easy pull-down of intact, functional protein complexes
  • No time-consuming preparation steps
  • Only isolate the proteins you want
  • Can be adapted for high-throughput applications

Featured Co-IP and pull-down categories

View technical and product selection guides for IP, co-IP and pull-down affinity beads and kits, including products based on Dynabeads magnetic beads and Pierce agarose resins, and including antibody-binding ligands (Protein A, G, L), biotin-binding ligands (streptavidin), and fusion tag–binding ligands (for His, GST, HA, and c-Myc).

Identify protein-nucleic acid interactions using magnetic bead-mediated immunoprecipitation. Optimized chromatin IP (ChIP) kits available, as well as kits for protein-RNA pull-down and related techniques.